In the casting of refractory shapes from finely divided refractory materials, it is a general practice to mix the refractory material with a binder and a suitable amount of a tempering agent, such as, water. The tempering agent is necessary so that the mixture will readily flow into the mold and to enable formability of the mixture. After the shape has been molded, it is usually fired at an elevated temperature to drive off the tempering agent and other volatiles, thus resulting in a relatively porous product. In many applications, high density refractory shapes are required; thus, reduction of the amount of tempering agent necessary for the mixture, would be extremely helpful in increasing the density of the final product.
Another problem that has arisen in the casting of refractory shapes, is the difficulty of removal of the shape from the mold cavity. Quite often, the green refractory shape has a tendency of adhering to the mold walls, thus, destroying the shape contours upon removal.
In the instant invention, the mix or the molds must be vibrated to achieve maximum density. The invention of vibration forming over conventional casting are numerous. Since the present invention can be supplied as a tempered mix, water amounts, types and temperature as well as mixing parameters are of no concern to the user. The present invention contains no cement; and so, pot life is no problem. Another difference between the present invention and conventional castables, is that castables must be allowed to achieve a set before the forms are removed. With vibration casting, the forms may be removed as soon as the vibration is stopped. The mixes of the present invention will not only support their own weight, but will support a considerable additional load without slumping.
U.S. Pat. No. 4,056,398 relates to a plastic refractory composition suitable for placement by vibrating techniques. The composition is based upon a carefully controlled addition of bentonite and tetrasodium pyrophosphate in combination with one or more aluminous materials.